Check valve for a piston pump

ABSTRACT

A check valve for a piston pump of a traction-controlled vehicle brake system includes hollow cylindrical valve seat part and a disk-shaped valve closing body, which is embraced by a spring clip and is secured to and guided against the valve seat part. The invention has the advantage that the check valve can be simply and inexpensively manufactured.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a 35 U.S.C. 371 application of PCT/DE 01/01721,filed on May 8, 2001.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The invention relates to a check valve for a piston pump, particularlyfor use in a piston pump of a hydraulic vehicle brake system that has atraction control apparatus.

2. Description of the Prior Art

A check valve of this kind has been disclosed, for example, by DE 41 07979 A1. The known check valve is disposed at one end of a piston that ispart of a piston pump; the piston pump is provided for supplying brakefluid to a hydraulic vehicle brake system that has a traction controlapparatus. The piston has an axial opening whose mouth constitutes avalve seat of the check valve. A ball disposed against the valve seatconstitutes a valve closing body of the known check valve. In anintrinsically known fashion, the ball that constitutes the valve closingbody rests in a sealed fashion against the valve seat when the checkvalve is closed and is lifted up from the valve seat when the checkvalve is open.

The expensive assembly of the known check valve during the assembly ofthe piston pump is disadvantageous; the known check valve cannot bepreassembled as a unit. Another disadvantage of the known check valve isthat a guide must be provided for the valve closing body.

SUMMARY OF THE INVENTION

In a check valve according to the invention, the valve closing spring isembodied as a spring clip which embraces the valve closing body, isattached to the valve seat part, and connects the valve closing body tothe valve seat part in a mobile fashion. The check valve according tothe invention has the advantage that its valve closing springsimultaneously constitutes a guide and a valve stroke limitation for thevalve closing body. The latter means that the spring clip limits adistance by which the valve closing body can be lifted up from the valveseat. The valve stroke limitation permits a short closing time of thecheck valve to be achieved. The check valve according to the inventioncan be simply and inexpensively produced out of only three parts, issuitable for miniaturization, and is thus suitable for use as an inletor outlet valve of a piston pump of a traction-controlled vehicle brakesystem. However, this is not the only potential application of the checkvalve according to the invention; it can, in principle, be used anywherethat backflow needs to be prevented. The check valve according to theinvention constitutes a subassembly whose parts are held together andwhich can be stored and installed as a unit.

Our embodiment of the valve closing body has a disk-shaped component andhas the advantage that when the check valve opens, it rapidly unblocks alarge flow cross section which lends the check valve favorable dynamicproperties.

The check valve according to the invention is provided as an inlet oroutlet valve of a piston pump, particularly for connecting to an end ofa piston of the piston pump. According to the invention, the piston pumpis particularly provided as a pump in a brake system of a vehicle and isused to control the pressure in wheel brake cylinders. Depending on thetype of brake system, these brake systems are referred to by theabbreviations ABS, TCS, ESP, or EHB. In the brake system, the pump isused, for example, to return brake fluid from one or more of wheel brakecylinders to a master cylinder (ABS) and/or for supplying brake fluidfrom a reservoir into one or more of wheel brake cylinders (TCS, ESP, orEHB). The pump is required, for example, in a brake system with a wheelslip regulation (ABS or TCS) and/or in a brake system used as a steeringaid (ESP) and/or in an electrohydraulic brake system (EHB). Wheel slipregulation (ABS or TCS) can, for example, prevent the wheels of thevehicle from locking when there is powerful pressure on the brake pedalduring a braking maneuver (ABS) and/or can prevent the driven wheels ofa vehicle from spinning when there is powerful pressure on theaccelerator pedal. In a brake system used as a steering aid (ESP), abrake pressure is built up in one or more wheel brake cylinders,independent of an actuation of the brake pedal or accelerator pedal, inorder, for example, to prevent the vehicle from swerving out from thepath desired by the driver. The pump can also be used in anelectrohydraulic brake system (EHB) in which the pump supplies brakefluid to the wheel brake cylinder(s) when an electric sensor detects anactuation of the brake pedal or in which the pump is used to fill areservoir of the brake system.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will be explained in detail below in conjunction with apreferably selected exemplary embodiment shown in the drawings, inwhich:

FIG. 1 shows an axial section through a piston pump with a check valveaccording to the invention; and

FIG. 2 shows an enlarged side view of the check valve from FIG. 1;

DESCRIPTION OF THE PREFERRED EMBODIMENT

The piston pump 10 shown in FIG. 1 is inserted into a hydraulic block12, which constitutes a pump housing and will be referred to as suchbelow. The hydraulic block 12, of which only the part surrounding thepiston pump 10 is shown in the drawing, contains a hydraulic controlcircuit of a traction-controlled vehicle brake system that is nototherwise shown. In addition to the piston pump 10, other hydrauliccomponents that are not shown, e.g. solenoid valves, are inserted intothe hydraulic block 12 and hydraulically connected to one another.

The hydraulic block that constitutes the pump housing 12 is providedwith a stepped pump bore 14 into which a cup-shaped sleeve 16 isinserted, which has a sleeve bottom 18 that is of one piece with it. Thesleeve 16 is produced by being deep-drawn from a metal sheet. A piston20 of the piston pump 10 is guided in an axially mobile fashion with onepart of its length in the sleeve 16 and with another part of its length,which protrudes from the sleeve 16, in the pump bore 14. The pump bore14 and the sleeve 16 constitute a piston guide 14,16.

The piston 20 is essentially comprised of two parts; it has abeaker-shaped outer part 22 into which a cup-shaped inner part 24 ispress-fitted over approximately half of its axial length. The outer part22 and the inner part 24 are produced as shaped parts by beingdeep-drawn from a metal sheet. The inner part 24 has an annular step 26with which it presses against an annular step 27 of the outer part 22.At one end, the inner part 24 has an end wall 28 that is of one piecewith it. The outer part 22 also has an end wall 30 that is of one piecewith it. An open end of the inner part 24 is oriented away from theouter part 22. The end wall 28 of the inner part 24 is provided with acentral opening 32 to permit the passage of brake fluid. In order toincrease abrasion resistance, the outer part 22 is hardened, at least inthe vicinity of its end wall 30, and no further machining is carriedout; a surface quality of the inner part 24 and the outer part 22 issufficient.

The piston pump 10 shown in FIG. 1 is embodied as a stepped piston pump.This means that the piston 20 is guided and sealed along a greaterdiameter inside the sleeve 16 than outside the sleeve 16 in the pumpbore 14 in the pump housing 12. Because it is embodied as a steppedpiston pump, the piston pump 10 has an annular chamber 34 encompassingthe piston 20 in the pump bore 14 and/or in the sleeve 16. A volume ofthis annular chamber 34 changes during a reciprocating stroke motion ofthe piston 20 and produces an aspiration of brake fluid even during adelivery stroke of the piston 20 of the piston pump 10.

A free edge 36 of the sleeve 16 is crimped inward; it secures the piston20 against the annular step 27 of its outer part 22 in the sleeve 16. Apiston restoring spring 38, which is embodied as a helical compressionspring, is inserted into the sleeve 16. The piston restoring spring 38is supported against the sleeve bottom 18 and presses against theannular step 26 of the inner part 24 of the piston 20 on the inside ofthe piston 20. The piston restoring spring 38 presses the piston 20against the circumference of a cam 39, which can be driven to rotate byan electric motor and is disposed at the end of the piston 20 protrudingfrom the sleeve 16. When the cam 39 is driven to rotate, it sets thepiston 20 into an axially reciprocating stroke motion.

A check valve 40 according to the invention, an enlarged depiction ofwhich is shown in FIG. 2, is connected to the end of the piston 20disposed inside the sleeve 16. The check valve 40 has a hollow,cylindrical valve seat part 42 with which it is press-fitted into thebeaker-shaped inner part 24 of the piston 20. This produces a force fitbetween the check valve 40 and the piston 20, which secures the checkvalve 40 in the inner part 24 of the piston 20. The valve seat part 42of the check valve 40 according to the invention rests against the endwall 28 of the inner part 24 of the piston 20, which is provided withthe central opening 32 for the passage of brake fluid. A terminatingedge of the valve seat part 42 oriented away from the end wall 28constitutes a valve seat 46 of the check valve 40. A cylindrical orcircular, disk-shaped valve closing body 48 of the check valve 40 isdisposed against the face of the valve seat 46 of the valve seat part42. The valve seat part 42 and the valve closing body 48 aremanufactured as injection molded plastic parts.

The valve closing body 48 is embraced by a spring clip 50, whichconstitutes a valve closing spring of the check valve 40. The springclip 50 is bent from a strip of sheet metal. For attachment to the valveseat part 42, the two ends of the spring clip 50 are bent inward atright angles and constitute detent elements 52 that engage in recessesin the outer circumference of the valve seat part 42. Arms 54 of thespring clip 50 extending in an axially parallel fashion along the outercircumference of the valve closing body 48 are provided with anundulation 56 in order for the arms 54 to be able to flex in aspring-elastic fashion in their longitudinal direction. The springbracket 50 has additional spring elasticity due to the elasticflexibility of its yoke 58, which extends across the end face 60 of thevalve closing body 48 oriented away from the valve seat part 42.

The spring clip 50 secures and guides the valve closing body 48 on thevalve seat part 42; it limits a valve stroke of the check valve 40, i.e.the distance by which the valve closing body 48 can be lifted up fromthe valve seat 46, and it presses the valve closing body 48 with aslight initial stress against the valve seat 46 so that the check valve40 is closed in its normal state and opens in the flow direction whenthere is a slight pressure difference. The check valve according to theinvention rapidly opens a large flow cross section, which is significantto the suction behavior of the piston pump 10 (dynamics).

The force fit 44 between the valve seat part 42 and the inner part 24 ofthe piston 20 assures that no brake fluid can bypass the check valve 40when flowing from a pump chamber 62 back into the outer part of thepiston 20. In addition, the force fit 44 secures the check valve 40 tothe piston 20 not only during operation of the piston pump 10 but alsobefore and during the assembly of the piston pump 10. This significantlyreduces the total cost for manufacturing the piston pump 10.

The check valve 40 according to the invention constitutes an inlet valveof the piston pump 10. In order to permit the entry of brake fluid,inlet openings 64 are let into a circumference wall of the outer part 22of the piston 20 of the piston pump 10. The inlet openings 64 permit aninner chamber 66 of the outer part 22 of the piston 20 to communicatewith the annular chamber 34 encompassing the outer part in the pump bore14. The annular chamber 34 is fed by an inlet bore 68, which is let intothe pump housing 12 radial to the pump bore 14. The brake fluid travelsfrom the inner chamber 66 of the outer part 22 of the piston 20, throughthe central opening 32 in the end wall 28 of the inner part 24, to thecheck valve 40 according to the invention, which constitutes the inletvalve of the piston pump 10.

An outlet from the pump chamber 62 of the piston pump 10 occurs by meansof a central opening 70 in the sleeve bottom 18; an edge of the centralopening 70 disposed on the outside of the sleeve bottom 18 constitutes avalve seat 72 of an outlet valve 74 of the piston pump 10. The outletabout 74 is embodied as a spring-loaded check valve. A helicalcompression spring serving as a valve closing spring 76 presses a valveball 78, which constitutes a valve closing body, against the valve seat72. The valve ball 78 and the valve closing spring 76 are inserted intoan axial blind bore 80 in a cylindrical stopper 82, which is placedagainst the sleeve bottom 18. The stopper 82 is fastened and sealed in apressure tight manner in the pump bore 14 with a circumferentialcaulking 84 of the pump housing 12. Brake fluid flowing out through theoutlet valve 74 escapes through radial conduits 86 arranged in a starpattern between the stopper 82 and the sleeve bottom 18, into an annularconduit 88 encompassing the sleeve 16 in the pump housing 12 and fromthere, through an outlet bore 90 let into the pump housing 12 radial tothe pump bore 14.

The foregoing relates to preferred exemplary embodiments of theinvention, it being understood that other variants and embodimentsthereof are possible within the spirit and scope of the invention, thelatter being defined by the appended claims.

What is claimed is:
 1. A check valve for a piston pump, comprising avalve seat part having a valve seat, a valve closing body thatcooperates with the valve seat, and a valve closing spring which pressesthe valve closing body against the valve seat, said valve closing springbeing embodied as a spring clip (50), which extends substantially acrossa diameter of the valve closing body (48), is fastened to the valve seatpart (42), and connects the valve closing body (48) to the valve seatpart in a mobile fashion.
 2. The check valve according to claim 1,wherein the spring clip (50) has detent elements (52) which engage inrecesses of the valve seat part (42).
 3. The check valve according toclaim 1, wherein the valve closing body (48) is embodied in the shape ofa disk.
 4. The check valve according to claim 3, wherein the valve seatpart (52) is embodied in the shape of a tube and has a flat valve seat(46).